Browning, Robert (1964). "Byzantine Scholarship". Past and Present (28): 7–8. doi:10.1093/past/28.1.3.
According to Joseph Genesius and Theophanes Continuatus between 829 and 833; Symeon the Logothete makes the caliph al-Mutasim and puts the invitation after the Islamic conquest of Amorium in the fall of 838, cf. Treadgold, Warren T. (1979). "The Chronological Accuracy of the Chronicle of Symeon the Logothete for the Years 813–845". Dumbarton Oaks Papers. 33: 162. doi:10.2307/1291437. JSTOR1291437.
Treadgold, Warren T. (1979). "The Revival of Byzantine Learning and the Revival of the Byzantine State". The American Historical Review. 84 (5). American Historical Association: 1245–1266 [p. 1259]. doi:10.2307/1861467. JSTOR1861467.
jstor.org
According to Joseph Genesius and Theophanes Continuatus between 829 and 833; Symeon the Logothete makes the caliph al-Mutasim and puts the invitation after the Islamic conquest of Amorium in the fall of 838, cf. Treadgold, Warren T. (1979). "The Chronological Accuracy of the Chronicle of Symeon the Logothete for the Years 813–845". Dumbarton Oaks Papers. 33: 162. doi:10.2307/1291437. JSTOR1291437.
Treadgold, Warren T. (1979). "The Revival of Byzantine Learning and the Revival of the Byzantine State". The American Historical Review. 84 (5). American Historical Association: 1245–1266 [p. 1259]. doi:10.2307/1861467. JSTOR1861467.